In opthalmology, systems for measuring the wave front aberration of an eye are known. In practice so-called Hartmann Shack sensors have become established for wave front measurement. With these sensors the wave front to be measured is imaged by a microlens array on to a light-sensitive detector as a dot pattern. If there are deviations of the detected wave front from an ideal wave front, owing to the aberration of the eye, this can be calculated from the detected dot pattern. A narrow light beam is directed on to the eye to be examined for this purpose and light is imaged on to the Hartmann Shack sensor after interaction with the eye.
Systems for measuring wave front aberrations are used in particular in the area of refractive surgery. It is known in this case to use systems which measure the aberration of an eye when the eye fixes on a stimulus appearing at an appointed distance. More recent systems allow calculation of the aberration of an eye by detecting aberrations during fixing on a stimulus which is observed at different distances. Calculation of the aberration is done on the basis of the aberrations detected for different stimuli.